1. Field of the Invention
The invention relates to a vehicle control apparatus, and more particularly, to a technology for limiting the number of times a driving force is increased through downshifting.
2. Description of Related Art
Electric automobiles and hybrid vehicles equipped with an electric motor as a drive source, as well as electric automobiles provided with a range extension function (range extender), are available. In many instances, these vehicles are not equipped with a stepped transmission that enables speed ratio modification. In such cases, the ratio between the revolutions of the drive source (for instance, an electric motor or engine) and axle revolutions, i.e. the speed ratio, need not be selected manually by the driver, to change the driving force of the vehicle thereby. In such vehicles, however, there is a need to provide the driver with the operating experience of changes in the driving force through shifting, as in ordinary vehicles equipped with an engine alone as the drive source. In order to meet that need, the shift range in some electric automobiles and hybrid vehicles is variable, and control is performed in such a way so as to obtain a travel characteristic according to a selected shift range.
However, enabling the driver to select the shift range makes it possible for the shift range to be modified based on an improper operation erroneously inputted by the driver. As an example of a measure for preventing such improper shifting, Japanese Patent Application Publication No. 9-242868 (JP 9-242868 A) discloses the feature of not accepting the input of a manual transmission instruction during a lapse of time from start of automatic shifting until a predefined time has elapsed.
In the case of an anomaly in an output system for outputting a shift instruction signal in a manual transmission mode, for instance in case of close-fail of a position switch for detecting the position of a shift lever, the shift instruction signal may in some instances be outputted a plurality of times within a short time, by the output system, in the manual transmission mode. The driving force of the vehicle may increase abruptly and the vehicle may experience a significant jolt, if a downshift instruction signal is outputted a plurality of times, within a short time, by the output system, in a manual transmission mode, and, accordingly, downshifting is performed a plurality times within a short time. However, JP 9-242868 A gives no consideration at all to an instance where a downshift instruction signal is outputted a plurality of times, within a short time, in a manual transmission mode.